In wireless, digital communications systems, transmission devices, often referred to as transmitters, comprising a Radio Frequency Digital-to-Analog Converter (RF-DAC) are used to transmit high-frequency, analog transmission signals, which transmission devices constitute a combination of a digital-to-analog converter and a mixer. A digital baseband signal is generally fed to such RF-DACs, which digital baseband signal is initially converted to an analog signal by the RF-DAC and then transformed to a prescribed carrier frequency.
In circuit arrangements of this kind in the form of an RF-DAC, it is necessary first to oversample the digital baseband signal before the digital-to-analog conversion and then to filter said signal using a digital low-pass filter. Steep level changes of the signal can be smoothed by these measures so that the emission of undesired interference signals is reduced. In such transmission devices that are intended to be designed for digital communications system having a high bandwidth, however, the circuitry outlay for implementing the oversampling and digital filtering of the baseband signal is very high because, amongst other things, the circuits used have to be operated at a high switching frequency. The high switching frequency of the circuits for processing the baseband signal can produce glitches, which promote the emission of undesired interference signals. During transmission of signals with a high bandwidth, interference signals can therefore be suppressed only insufficiently. The RF-DAC also has to operate at a high clock frequency in order to be able to implement a correspondingly high sampling rate. This also promotes the production of glitches.